The invention relates to an apparatus for dosed mixing of pourable material components, in particular a gravimetric dosing apparatus. Further, the invention relates to a plastics processing machine having such an apparatus. Pourable material components are to be understood as comprising, in particular, bulk material, but also material components capable of flowing, for example a liquid material component.
When manufacturing plastic products, usually the used material components are fed in the form of a bulk material, in particular a granulated material or a powder. For example, it is known to feed different material components one after another to a weighing container, until in each case that weight of the weighing container is reached, which is necessary for the allotted proportion of quantity of the material component. When all material components are present in the designated proportions in the weighing container, for example, a delivery flap or a gate is opened, and the material is transferred into a mixing container. In the mixing container, a mixer provides for a homogenous mixing of the material components. The mixing container is in turn connected to a processing machine, e.g., an extruder. An apparatus of the kind described above is known from EP 0 959 982 B1.
When the performance of such a conventional plastics processing machine is to be increased, the throughput of respective feeding devices for the material components must be increased in order to be able to more rapidly fill the weighing container. In order to be able to achieve a higher throughput, while maintaining the same accuracy of the material components, which are fed by time controlled opening of the feeding device, considerable additional constructive efforts are required at the feeding devices. Moreover, the weighing of each added material component requires a suspension of the filling procedure of the weighing container, and, thus, is time consuming. Furthermore, the weighing procedure itself requires a certain amount of time. In order to achieve an increase of the performance by an increased throughput of the feeding devices in an efficient manner, thus, the weighing container would also have to be made larger in order to avoid an unreasonably frequent, time consuming weighing procedure. Furthermore, a weighing device suitable for a larger weight would have to be applied.
From DE 38 18 637 A1, an apparatus for mixing material components is known, wherein, for each material component, a weighing container of its own is provided, and wherein a movable collecting container approaches the filled weighing containers one after another and receives the respective weighed material component. Afterwards, all material components received in the collecting container are discharged to a mixer. It is a disadvantage that such a machine requires a large amount of space, and that the movable collecting container is technically complex.